Aortic calcification, also called aortic sclerosis, is a buildup of calcium deposits on the aortic valve in the heart. This often results in a heart murmur, which can easily be heard with a stethoscope over the heart. However, aortic calcification usually doesn't significantly affect the function of the aortic valve.
In some cases, though, the calcium deposits thicken and cause narrowing at the opening of the aortic valve. This impairs blood flow through the valve, causing chest pain or a heart attack. Doctors refer to such narrowing as aortic stenosis.
Aortic calcification typically affects older adults. But when it occurs in younger adults, it's often associated with an aortic valve defect that is present at birth (congenital) or with other illnesses such as kidney failure. An ultrasound of the heart (echocardiogram) can determine the severity of aortic calcification and also check for other possible causes of a heart murmur.
At present there is no specific treatment for aortic calcification. General treatment includes the monitoring for further developments of heart disease. Cholesterol levels are also checked to determine the need for medications to lower cholesterol in the hope to prevent progression of aortic calcification. If the valve becomes severely narrowed, aortic valve replacement surgery may be necessary.
The aortic valve area can be opened or enlarged with a balloon catheter (balloon valvuloplasty) which is introduced in much the same way as in cardiac catheterization. With balloon valvuloplasty, the aortic valve area typically increases slightly. Patients with critical aortic stenosis can therefore experience temporary improvement with this procedure. Unfortunately, most of these valves narrow over a six to 18 month period. Therefore, balloon valvuloplasty is useful as a short-term measure to temporarily relieve symptoms in patients who are not candidates for aortic valve replacement.
Patients who require urgent noncardiac surgery, such as a hip replacement, may benefit from aortic valvuloplasty prior to surgery. Valvuloplasty improves heart function and the chances of surviving non-cardiac surgery. Aortic valvuloplasty can also be useful as a bridge to aortic valve replacement in the elderly patient with poorly functioning ventricular muscle. Balloon valvuloplasty may temporarily improve ventricular muscle function, and thus improve surgical survival. Those who respond to valvuloplasty with improvement in ventricular function can be expected to benefit even more from aortic valve replacement. Aortic valvuloplasty in these high risk elderly patients has a similar mortality (5%) and serious complication rate (5%) as aortic valve replacement in surgical candidates.
Transarterial aortic valve replacement is a new procedure where the aortic valve is replaced with a self-expanding nitinol or balloon-expandable valve structure. Such procedures benefit from a smooth non-calcified circumference to attach the new valve. Large calcium deposits may induce leaks around the valve preventing a firm consistent attachment of the valve to the aorta. Thus there is a need for a calcium free valve bed to attach such self-expanding valves.
An alternative method and system for treating stenotic or calcified aortic valves is disclosed and claimed in co-pending U.S. application Ser. No. 12/611,997, filed Nov. 11, 2009 for SHOCKWAVE VALVULOPLASTY SYSTEM. As described therein, a balloon is placed adjacent leaflets of a valve to be treated and is inflatable with a liquid. Within the balloon is a shock wave generator that produces shock waves that propagate through the liquid and impinge upon the valve. The impinging shock waves soften, break and/or loosen the calcified regions for removal or displacement to open the valve or enlarge the valve opening.
The approach mentioned above provides a more tolerable treatment for aortic stenosis and calcified aortic valves than the previously performed aortic valve replacement. It is also a more effective treatment than current valvuloplasty therapy. For patients undergoing transaortic or catheter based aortic valve replacement, this new method can soften, smooth, and open the aortic valve annulus more effectively than current valvuloplasty and prepare the area for a catheter delivered valve.
In the shock wave valvuloplasty described above, the impingement intensity of the shockwaves diminishes as a function of the distance from the shock wave origination point to the valve. More specifically, the impingement intensity of the shock waves is inversely proportional to the square of the distance from the shock wave origination point to the valve. Hence, when applying the shock waves, it would be desirable to maximize their effectiveness by being able to minimize the distance between the shock wave source and the valve location being treated at that moment.
Similar issues are present in angioplasty. There, a calcified region of a vein or artery may extend over some longitudinal distance of the vein or artery. A point shock wave source within an angioplasty balloon, in such instances, would not be uniformly effective across the extent of the calcified region because of the varying distance from the shock wave source to the various portions of the calcified region.
The present invention addresses this and other matters of importance in providing the most efficient and effective valvuloplasty and angioplasty treatment possible.